In which cases is it recommended to write unit tests for code?

It is recommended to write unit tests for code that:

• Performs important business logic where errors are critical.
• Contains complex algorithms or conditions that are difficult to verify manually.
• Changes or evolves frequently to quickly identify regressions.
• Is reused in different parts of the application.

Writing unit tests helps ensure that individual parts of the code work correctly and simplifies maintenance and refactoring.